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...cies during the [https://en.wikipedia.org/wiki/Cambrian_explosion Cambrian explosion], about 542 million years ago.

...planet about 3.75 billion years ago. Complex life began with the Cambrian explosion about six hundred million years ago; the Age of Mammals began about sixty-f

...l Earth]]", and it is of particular interest as it precedes the [[Cambrian explosion]] in which multicellular life forms began to proliferate about 530-540 mill Since the [[Cambrian explosion]] there have been five distinctly identifiable [[Extinction event|mass exti

...neages that subsequently became extinct. Various triggers for the Cambrian explosion have been proposed, including the accumulation of [[oxygen]] in the [[atmos

...Earth]]", and is of particular interest because it preceded the [[Cambrian explosion]], when multicellular life forms began to proliferate. The Proterozoic Bios Following the [[Cambrian explosion]], about 535 mya, there have been five [[Extinction event|mass extinct